The leak-test dye in the A/C system shines what color when illuminated by a specific light?

The leak-test dye used in A/C systems is designed to react to ultraviolet (UV) light. When exposed to UV light, the dye fluoresces, allowing technicians to easily identify the presence of leaks within the system by the bright glow that contrasts against the darker surroundings. This property makes it a valuable tool during diagnostics, as the visible fluorescence can lead to quicker and more efficient troubleshooting of refrigerant leaks.

Other options, while they may be associated with various detection methods or technologies, do not produce the same distinctive visual cue as the UV-reactive dye. Infrared light, for instance, does not activate the fluorescence of the dye, while blue lasers and mercury vapor technologies serve different purposes in other contexts and are not standard in leak detection for A/C systems. Only the UV light effectively illuminates the dye and enhances visibility for leak detection.